Preparation And Characterization Of Novel N-hybrid Bipolar Host Materials

The purpose of this article is to design and synthesize some small molecular phosphorescent materials with high triplet energy level,good film-forming ability and balanced carrier transport for solution preparation.(1)Four phosphorescent host Materials,named PyDFDPA,PyDFPNA,PyDFPPA and PyDFCz,were synthesized,with pyridine as the core material and triphenylamine as arm.Firstly,the pyridine group was introduced on the fluorene skeleton,as the molecular core,and then the triphenylamine or carbazole group was attached into the skeleton to facilitate the hole/electron charge injection and transmission.The resultant full color organic light-emitting diodes(OLEDs)of blue,green,and orange phosphorescent devices were fabricated through simple solution process method.With the pure host of PyDFPPA,the blue devices show high efficiency of 18.5 cd/A.The orange phosphorescent devices from PyDFPNA cohost also show high efficiency with a maximum luminous efficiency of 37.3 cd/A in the high brightness region of 3000 to 30000 cd/m2,making it among the most efficient orange OLEDs from solution processed single-emissive layer structure.Moreover,the efficiencies roll-off has been greatly depressed in this series of devices,especially for the green and orange phosphorescent devices with 2.94% and 3.21%,respectively,from the maximum to the high brightness of 10000 cd/m2?(2)Three 4,5-diazofluorene-based electron acceptor materials,named DTPANF-TPA,DTPANFTPA and DTPANF-TT,were synthesized through the Friedel-Crafts reaction of DTPANF-OH and triphenylamine,or carbazole and dithiophene,respectively.In order to increase the solubility of the target compound of DCzNF-POA,a DCzNF-OH was introduced as the arm,and phenoxazine as the core.The four compounds DTPANF-Cz,DTPANF-TPA,DTPANF-TT and DCzNF-POA all have very high glass transition temperatures of 211°C,210 °C,209 °C and 215 °C,respectively.In addition,all the compounds show excellent film-forming ability,with the root mean square roughness of 0.48,0.38,0.73 and 0.47 nm,respectively.(3)Three simple D-A-D-typed compounds,m-CzSO,p-CzSO and 3-CzSO,were synthesized,containing diphenylsulfoxide and carbazole moieties,with the triplet energy levels of 2.87 eV,2.59 eV,and 2.60 eV,respectively.In addition,this series of compounds show good film-forming ability,with the root mean square roughness of 0.57,0.56 and 0.45 nm,respectively.